Abstract
The dissolution of the (111) surface of Cu single crystals was studied as a function of concentration of oxidizer (NH4)2S2O8 and complexing agent NH4OH in Young’s solution ((NH4)2S2O8–NH4OH–NH4Br). The etching was carried out for 10 s at 280 K with a crystal rotation 4 s−1 using the rotation disc method. The dissolved depth of matrix surface S was obtained by two-beam interferometric measurement of the step height produced at the boundary between the masked surface and the exposed surface to the etching. The width h and depth d of etch pits formed at edge dislocation sites on the exposed surface were determined by replica electron microscopy. The dissolved quantities along lateral and longitudinal directions at dislocation H and D were determined from S, h and d, respectively.
As the concentration of (NH4)2S2O8 or NH4OH in the etchant was increased, the following features were observed: (a) the lateral dissolution at the dislocation site, H, increased monotonically, (b) the longitudinal dissolution at the dislocation site, D, attained a maximum value at the intermediate concentration and (c) the matrix dissolution, S, increased slightly. These results were discussed on the basis of the two-dimensional nucleation theory of crystal dissolution.
